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Reciprocatory piston and cylinder machines

  • US 4,102,608 A
  • Filed: 12/22/1976
  • Issued: 07/25/1978
  • Est. Priority Date: 12/24/1975
  • Status: Expired due to Term
First Claim
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1. A vacuum pump comprising:

  • a cylinder having a first portion closed at one end and a second portion contiguous with, but of smaller diameter than, the first portion;

    a piston having a head portion slidable in the first cylinder portion and a second piston portion of smaller diameter than the head portion and slidable in the second cylinder portion, said piston head portion having a front face facing the closed cylinder end and an annular back face;

    a gas inlet for inlet of gas to the interior of the first cylinder portion between the front face of the piston head portion and the closed cylinder end on reciprocation of the piston;

    a first exhaust duct for exhaustion of gas from the interior of the first cylinder portion ahead of the piston head portion by pumping action of the front face of the piston head portion;

    a one-way valve in said first exhaust duct operable by gas pressure thereon to permit exhaustion of gas from the interior of the first cylinder portion ahead of the piston head portion but closable against reverse gas flow;

    an exhaust means for exhaustion of gas from the interior of the first cylinder portion behind the piston head portion by pumping action of the back face of the piston head portion; and

    a gas transfer passage for transfer of gas from said interior of the first cylinder portion ahead of the piston head portion to the interior of the first cylinder portion behind the piston head portion by pumping action of the front face of the piston head which gas transfer passage is capable of said transfer of gas at gas pressures lower than required to open said one way valve.

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